Sex in the tropics: reproduction of Chthamalus malayensis Pilsbury (Class Cirripedia) at the equator

Abstract

The reproduction of a key intertidal space occupier, the barnacle, Chthamalus malayensis, was examined over a 13-month period. The reproductive cycle of C. malayensis was studied at three shores (Singapore, east and west coast of Malaysia) near the centre of its geographical range. Testes, vesiculae seminales, ovaries and embryos were scored for their stages of development. Although, in general, C. malayensis contained gonads throughout the year, the timing and level of peak development varied between the three shores. Embryos were present throughout the year in west Malaysia but were absent for 4–5 months in east Malaysia (June–August and October) and Singapore (February, April and August). Variations in the reproductive cycles and brooding were not clearly linked to the timing of monsoons. The lack of seasonal peaks in breeding may be attributed to the relatively constant climatic conditions experienced near the equator.

Notes

Acknowledgements

This research was supported by National University of Singapore research grant R-154–000–160–101. We would like to thank N.F. Ramsay, H.H. Tan, C.P. Lim and A.P.K. Ng for assistance in the field. We would also like to thank the meteorological stations of Singapore and Malaysia for providing the climate data. Permission to collect samples in Malaysia was kindly granted to R.M. O’Riordan by the Economic Planning Unit (permit number: 40/200/19 SJ.1048). We are grateful to the three anonymous reviewers for their constructive comments on the manuscript.

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